This invention relates to the counting of particles, and more particularly to method and apparatus for counting seeds as they are delivered from a seed planter to the soil.
In practice, a plurality of separate seed planters are drawn over the ground by a tractor, the planters being spaced apart laterally according to the desired spacing between plant rows. Each planter is supplied with seeds from its own reservoir and each delivers its seeds to the soil independently of the others.
In the planting of seeds it is important that all of the planters deliver seeds the same feed rate. It is also important to be able to ascertain when any given planter is failing to deliver seeds to the soil, as when the supply reservoir becomes empty, or the seed delivery mechanism becomes plugged or inoperative, or because of some other malfunction of the planter.
Seed monitors and counters have been provided heretofore in an effort to achieve the foregoing objectives. One such type of monitor and counter functions by dropping seeds by gravity onto a spring loaded, pivoted plate which thereupon is pivoted to effect closure of the contacts of a switch in an electric counting circuit. This type of monitor is restricted in use to the counting of seeds of sufficient weight as to effect pivoting of the plate sufficiently to operate the switch. Moreover, it is susceptible of significant errors in counting, since the plate is caused to pivot under the influence of jars and jolts as the seed planting equipment travels over the uneven terrain of the planting area. Thus, it can falsely give indication that seeds are being planted even though no seeds are being delivered to the soil.
Another type of seed monitor and counter functions by dropping seeds by gravity vertically downward through a tube across which is provided a single horizontal beam of light, and detecting the resulting decrease of light intensity by a photocell. The beam of light has a vertical thickness many times greater than the thickness of seeds to be counted, and the photocell has a correspondingly large vertical field of detection. Accordingly, this type of seed counter is incapable of counting a large variety of types of seeds with sufficient accuracy to be of practicable utility. Indeed, its use is limited to the counting of seeds of a predetermined narrow range of sizes, because a plurality of seeds of smaller size can pass through the beam simultaneously and only be counted as one seed, and seeds of larger size cannot pass through the tube since the tube is restricted in width to the width of the single light beam.